The difficulty in making the translation between MAD during the Cold War and cyber is that it's so difficult.... There are two difficulties, really. You have to be able to assign attribution—a deterrent requires assigning attribution. Secondly, cyber is so difficult to control. The Stuxnet virus, for example, took out the centrifuges in Iran, but also, I believe, took out centrifuges in Germany—in places that the United States and Israel didn't want. So you can't really control it as a domain of warfare.
While I'm saying that Canada needs to think about whether cyber would be a domain of warfare, we also have to keep in mind that there are real downsides to using that tool.